This invention is a stylus for entering hand drawn letters or forms into a computer system, and more specifically is a writing instrument coupled to ultrasonic and IR transmitters which allow the system to continuously determine the position of the stylus.
There has long been a need in the industry for a device for efficiently and conveniently entering handwritten material into a computer. An example of this application would be for a person to sign his name on a sheet of paper in a normal and natural way, and simultaneously have the signature appear on a terminal and be stored in memory.
One well known method is to use sound transmitters and sound receivers to send audio waves between the stylus and two points on the writing surface, typically two corners. The delay of the sound waves between the stylus and the two corners allows the triangulation of the position of the stylus. However, none of the known devices for accomplishing this method are satisfactory.
One embodiment uses a spark gap mounted on the writing instrument to generate the sound wave, but this embodiment is unsatisfactory. The external high voltage spark gap is inconvenient and possibly dangerous. The system requires a cord to be attached to the stylus to supply the high voltage, which would be an inconvenience, especially when writing over a large writing surface. The shock wave produced by the spark is audible and a possible distraction to the user, and the sound produced by this method has a broad range of frequencies so the receiver can not be narrowly tuned to avoid noise. A device which uses a spark gap is described in a June 1970 IEEE Transactions On Computers article by A. E. Brenner and P. de Bruyne entitled A Sonic Pen: A Digital Stylus System, and in another December 1986 IEEE C G & A article by Pieter de Bruyne entitled Compact Large Area Graphic Digitizer for Personal Computers. Another is described in U.S. Pat. No. 3,626,483 by Whetstone et al entitled Spark Pen.
The Sonic Pen of Brenner was made cordless by using two stationary spark generators and a microphone in the moveable stylus. In this configuration, high voltage need not be delivered to the stylus. The drawbacks are the noise of the spark generators, and the necessity of pulsing the transmitters alternately, which reduces to half the number of position readings per unit of time.
Another element the stylus must have is a means for automatically signaling to the system, without any action required on the part of the writer, when the writing instrument is in contact with the writing surface. This would take the form of a position or pressure sensor mechanically coupled to the point of the writing instrument. Without this feature, the entrance of hand drawn script, block letters and drawings into the system would be very difficult. Stylusses having some elements of this invention but lacking this particular feature are described in a 1966 article in the Proceedings - Fall Joint Computer Conference by Lawrence G. Roberts entitled The Lincoln Wand, and in a Sept. 9, 1985 article on page 84 of the Electronic Engineering Times headlined 3-D Ultrasonic Input System Competes With Mouse, Tablet.
The device described in European Pat. No. A 159 498 is cordless and has a contact sensor, but it does not use sonic triangulation and is therefore limited to use with a particular magnetic tablet.
In conjunction with the other features, it would be desirable for the stylus to have function switches. These could indicate to the system, for example, what color the line is being drawn in, whether the line is dashed or solid, whether the stylus is being used as a pen, an eraser or a pointer, etc. It is not novel to put function switches in an electronic system as in FIG. 4 of the above referenced Brenner and Bruyne article. The novelty in this invention is that the switches are mounted on the stylus so that the operator need not take his hands and eyes away from the writing surface while changing functions. An example of a stylus having function switches is described in Technical Report No: SPD-TR2, dated Jan. 1985, published by Scriptel Corp., 3660 Parkway Lane, Hilliard, Ohio 43026. However, this device lacks most of the other features described above, and can not be used for the purpose of this invention. Furthermore, normal writing involves the use of the wrist and fingers. A mouse or puck, as shown in this Scriptel report, does not have the look and feel of a pen or pencil, and can not be used in the normal way as a writing instrument.
What is required is a stylus that will allow normal writing or pointing on any surface, and simultaneously will enter the result into memory.